Canned food is a convenient food for people's daily life. Bad quality or spoilage can cause damage to the body. The choice of canned food should be focused on three words: "look", "calculate" and "check".

 

"See" is to see the appearance of the logo and content. The surface of the tin can be cleaned without rust, the bottom and the cover are slightly concave, the seam and the bottom roll are not damaged, the close of the seal is a good can; the glass canned cover is slightly concave, the content is not cloudy, no precipitation, no color change, the shape of the block, the soup withdrawing many are the qualified products, and conversely, the tank cover and the tank body are not clean. Spot rust, with cracks, edges and sunken perforations, the solder is not complete, the liquid juice is not suitable to purchase; there is no hard code number on the lid, and there is no factory date and site name on the label paper, so the quality of the tin can not be guaranteed. For example, there is no "registration" two words on the trademark, indicating that it is not passed. The food factory approved by the industry and Commerce Department is best not to buy. The food in the tank is discoloured, cloudy and precipitated. It may be improper in the process of transportation and storage, the decomposition of food fat, the conversion of sugar, the deterioration of the quality, and most of the color, fragrance and taste of the canned canned canals. Tin and tin in the bottom of the tank and tank have exfoliation and iron exposure, with iron rust and iron sulfide spots, tin small pieces or internal flow glue in the tank. Heavy metals are often high in content and should not be eaten.

 

"Calculate" is to calculate the shelf life and calculate the factory name.  In order to ensure that the canned can not be fat to hear, not leak under normal transportation and storage conditions, keep the original quality, the human food is harmless, the state stipulates the time limit for all kinds of canned food, generally speaking: 8 months of fresh orange juice, sugar water bayberry, fresh grapefruit juice, steamed prawns, peanuts and so on; one year with ketchup, sugar water litchi, sugar water Plum, fresh pineapple juice, concentrated grapefruit juice, concentrated lemon juice, sour cucumber, eggplant sauce, sugar water carambola and so on; one and a half year and a half lunch meat, ham lunch meat, sugar water hawthorn, and so on; two years of sugar water orange, green knife fish, mushroom, sugar water pineapple, sugar water pear, sugar water peach, sugar water apricot, sugar water apple and sweet cherry cherry, Sugar grape, sugar begonia, hawthorn sauce, oil-soaked eel, oil-soaked pomfret, oil-soaked herring, oil-soaked beef, steamed mutton, bacon beef, bacon mutton and so on. The retention period is calculated from the date of production printed on the label paper, and the two is from the hard code code of the lid. If the hard code batch number is 9712161, that is, the tin can be produced in class 1 in December 16, 1997. According to this date, we can calculate the time to stay in each of the circulation links, and do not purchase if the time limit is above the above.

 

The factory name of the factory site can be calculated according to the uniform code given by the whole nation. Beijing A, Shanghai B, Liaoning C, Jilin D, Heilongjiang E, Inner Mongolia, Ningxia F, Hebei, Tianjin G, Shandong H, Henan I. Su, Qinghai X, Xinjiang, Tibet Y, Taiwan Z. Each canned food factory also has code names, such as Yantai canning factory H1, Qingdao egg factory H2, Ji'nan meat joint factory H3, Ji'nan egg factory H4, etc. Therefore, the English letter of hard code is H2, can be calculated out of Shandong Qingdao egg factory production canned, know the product factory name, easy to buy canned food. Of course, the product name also has a code name, because in practical life, practical value is not big, here is not to repeat.

 

"Inspection" is to test whether the canned spoilage. When the pressure inside the can is greater than the air pressure, the bottom of the two can expand and protrude, which is called fat hearing. The reason for the fat hearing is that it is not thoroughly germicidal in the process of canned production, or the bacteria reinvade the canned can, produce the gas inside, produce carbonated gas, cause fat listening, which is called fat and fat listening, also called true fat, and two is canned food with high acidity, combined with the tin layer of the head of the horse mouth iron, or the tin layer bruised. The organic acid in the substance has chemical reaction with iron, releasing hydrogen to form fat listening, which is called chemical fat listening; three is excessive content and fat hearing is called physical fat listening. The first two kinds of fat listening, confirmed that the system head has been corrupt and increased the content of heavy metals in the food, can not buy food, the latter is called false fat, the food in the tank does not deteriorate, can be eaten. So, how do these three fat listens judge? It can be inspected by percussion, pressing and perforation. It belongs to bacterial and chemical fat. Knocking is empty. When pressed, it is not easy to press down. Sometimes pressing down will also expand, and gas will run out after perforation. Physical fat listening to tap has real sound. When pressed, it can often form a dent, do not restore the original state, and perforate without gas running out.